Animal species, mammals, etc. Mammals, species of mammals, groups of mammals, cloacae, marsupials, placentals, carnivores, rodents, ungulates, edentulous, cetaceans, primates

MAMMALS
animals (Mammalia), class of vertebrates, most famous group animals, including more than 4600 species of world fauna. It includes cats, dogs, cows, elephants, mice, whales, people, etc. In the course of evolution, mammals have carried out the widest adaptive radiation, i.e. adapted to a variety of ecological niches. They inhabit polar ice, forests of temperate and tropical latitudes, steppes, savannahs, deserts and reservoirs. With a few exceptions (such as anteaters), their jaws are armed with teeth, and mammals can feed on meat, plants, invertebrates, and even blood. They range in size from the tiny pig-bearing bat (Craseonycteris thonglongyai), which is only approx. 29 mm and weighing 1.7 g, to the largest animal known to science - the blue whale (Balaenoptera musculus), reaching a length of approx. 30 m with a mass of 190 tons. Only two fossil brontosaur-like dinosaurs could compete with him. The length of one of them - Seismosaurus - is at least 40 m from the nose to the tip of the tail, but it weighed, according to some experts, approx. 55 tons, i.e. three times smaller than the blue whale. The second dinosaur, Ultrasaurus, is known from a single pelvic bone, but is thought to have been both longer and heavier than the blue whale. However, until this is confirmed by additional fossil remains, the blue whale remains the champion among all animals that have ever inhabited the Earth. All mammals have a series characteristic features their class. The class name Mammalia comes from lat. mamma - female breast, and is associated with the presence in all animals of glands that secrete milk. The term was first used in 1758 by the Swedish botanist Linnaeus in the 10th edition of his book The System of Nature. However, the scientific definition of mammals as a separate group was given even earlier (1693) by the English botanist and zoologist J. Ray in his work Methodological Review of the Origin of Quadrupeds and Snakes, and the everyday view of animals as a group of closely related creatures was formed at the dawn of human history.
Origin. Basic building plan modern mammals was inherited by them from their reptile ancestors, the so-called. synapsids, or animal-like lizards. The age of their oldest known remains is approximately 315 million years, which corresponds to the Pennsylvanian (Upper Carboniferous) period. It is believed that synapsids appeared soon after the appearance of the very first reptiles (anapsids), in the Mississippian (Lower Carboniferous) period, i.e. OK. 340 million years ago, and died out approx. 165 million years ago, in the middle of the Jurassic. The name "synapsids" indicates the presence of a pair of holes in the skull, one on each side behind the orbit. It is believed that they made it possible to increase the mass of the jaw muscles, and, consequently, their power in comparison with animals without such temporal fenestrae (anapsids). Synapsids (class Synapsida) are divided into two orders - pelycosaurs (Pelycosauria) and therapsids (Therapsida). The direct ancestors of mammals was one of the suborders of therapsids - small predatory reptiles cynodonts (Cynodontia). In their various families and genera, in one way or another, the signs of both reptiles and mammals were combined. It is assumed that at least the most evolutionarily advanced representatives of cynodonts possessed such features of animals as the presence of wool, warm-bloodedness, and the production of milk to feed the young. However, paleontologists do not build their theories on assumptions that are not supported by facts, in particular fossilized bones and teeth, which mainly remain from extinct vertebrates. Therefore, in order to distinguish reptiles from mammals, they use several key skeletal features, namely the structure of the jaws, the structure of the jaw joint (i.e., the type of articulation of the lower jaw to the skull), and the osseous system of the middle ear. In mammals, each branch of the lower jaw consists of a single bone - the dentary, and in reptiles it includes several more, including the so-called. articular. In mammals, the jaw joint is formed by the dentary of the lower jaw and the squamous bone of the cranium, while in reptiles it is formed by the articular and quadrate bones, respectively. Mammals have three bones in the middle ear (hammer, anvil, and stirrup), while reptiles have only one (the homologue of the stirrup called the style). Two additional ear bones arose from the quadrate and articular bones, which became the anvil and malleus, respectively. Although it is possible to build a whole sequence of synapsids, increasingly approaching mammals, up to almost complete resemblance to them in appearance and biology, the emergence of animals as a separate group is considered associated with the transformation of the reptilian type of the jaw joint, which moves from an articular-square position to an articulation between dentary and squamosal bones. Apparently, this happened in the middle of the Triassic period, approximately 235 million years ago, however, the earliest fossil remains of true mammals are known only from the end of the Triassic, i.e. im ok. 220 million years.
GENERAL CHARACTERISTICS OF MAMMALS
Some parts of the mammalian skeleton, especially the skull, are simpler than those of their reptile ancestors. For example, as already mentioned, each branch (right and left) of their lower jaw consists of one bone, and in reptiles - of several. In animals, the upper jaw (the intermaxillary bone in front and the maxillary bone in the back) is completely fused with the cranium, while in some reptiles it is connected to it by movable elastic ligaments. In mammals, the upper teeth are found only on the premaxillary and maxillary bones, while in primitive vertebrates they may also be on other bony elements of the roof of the oral cavity, including the vomers (near the nasal passages) and the palatine bones (near the maxillary). Mammals usually have two pairs of functional limbs, but some aquatic forms, such as whales (Cetacea) and sirens (Sirenia), have retained only the front. All animals are warm-blooded and breathe. atmospheric air. From all other vertebrates, with the exception of birds and crocodiles, they differ in a four-chambered heart and a complete separation of arterial and venous blood in it. However, unlike birds and crocodiles, mammalian mature red blood cells (erythrocytes) lack nuclei. With the exception of the most primitive members of the class, all mammals are viviparous and feed their young with milk produced by the mammary glands of the mother. Primitive animals, or monotremes, such as the platypus, lay eggs, but the young that hatch from them also feed on milk. In some species they are born, although fully formed, but naked (without hair) and helpless, and their eyes remain closed for some time. In other animals, especially ungulates (goats, horses, deer, etc.), cubs are born completely dressed in wool, with open eyes and almost immediately able to stand and move. In marsupials, such as kangaroos, cubs are born underdeveloped and endured for some time in a pocket on the mother's stomach.
Wool. The presence of wool covering the body is a distinctive feature of animals: only they form hair, i.e. filamentous keratinized outgrowths of the skin (epidermis). The main function of the coat is to insulate the body, facilitating thermoregulation, but it also serves many other purposes, in particular, it protects the skin from damage, can mask the animal due to its color or configuration, or demonstrate its gender. In many mammals, the hair in certain parts of the body has changed significantly and specialized in the course of evolution, turning, for example, into protective quills of a porcupine, rhinoceros horn, vibrissae (sensitive "whiskers") of cats and winter "snowshoes" (leg trim) of a hare. Individual hairs are in most cases cylindrical or oval in cross section, although in some species they are practically flat. Microscopic examination reveals that the hair shaft (above and just below the skin) is a compact, flexible rod composed of hardened dead cells. A typical trunk consists of three concentric layers: a central spongy core formed by loosely lying rectangular cells, often with small layers of air between them, a middle cortical layer that makes up the main part of the hair and is formed by spindle-shaped cells longitudinally located close to each other, and a thin outer skin ( cuticle) of scaly, overlapping cells, the free edges of which are directed towards the free end of the hair. Delicate primary hairs of a human fetus (lanugo), and sometimes a small fluff on the body of an adult, are devoid of a core. Hair cells form under the skin inside the hair follicle (follicle) and are pushed outward by new cells that form underneath. As you move away from the root, i.e. source of nutrition, the cells die and are enriched with keratin - an insoluble protein in the form of long thin fibers. Keratin fibers are chemically bonded to each other, which gives the hair strength. Hair color depends on several factors. One of them is the presence of pigments (coloring substances) called melanins. Despite the fact that the name of these pigments comes from the word "black", their color varies from yellow to red, brown and black. Melanins can appear in individual hair cells as they grow and move away from the follicle. The presence or absence of melanin, its color and quantity, as well as the proportion of air layers between the cells of the stem together determine the whole variety of hair colors. In principle, we can say that its color depends on the absorption and reflection of light by melanin (mainly the cortical layer) and its scattering by the walls of the air layers of the core. For example, black hair contains optically dense, very dark melanin both in the cortex and in the core, so it reflects only a very small part of the light rays. In contrast, the polar bear's fur is completely devoid of pigment, and its color is determined by the uniform scattering of light. The diversity of the hair structure is primarily associated with the shape of the cuticular cells and the location of the core cells. Specific animal species tend to be characterized by a particular coat structure, so a microscope can usually determine its taxonomic nature. A notable exception to this rule is the 150 species of shrews of the genus Crocidura with virtually identical hair. Species determination by microscopic features of hair is currently being replaced by more accurate methods based on the study of DNA and karyotypes (chromosome sets). Hair covering the body is generally divided into two types based on length and structure. Some of them are guard - long, shiny, relatively coarse. They are usually surrounded by one and a half to two times shorter undercoat hair. True seals (family Phocidae), also called earless seals, are covered mainly with coarse outer hair with a sparse undercoat. Fur seals, on the other hand, have a very thick undercoat. They belong to the family of eared seals (Otariidae), which also includes sea lions with the same skin as real seals.

Teeth , present in the vast majority of mammals, are solid structures that develop from special connective tissue (mesoderm) cells - odontoblasts and consist mainly of calcium phosphate (apatite), i.e. chemically very similar to bones. However, calcium phosphate crystallizes and combines with other substances in different ways, so that various dental tissues are formed as a result - dentin, enamel and cementum. Basically, a tooth is made up of dentin. (Elephant tusks and, accordingly, ivory are solid dentin; a small amount of enamel that first covers the end of the tusk is quickly erased.) The cavity in the center of the tooth contains the “pulp” that feeds it from soft connective tissue, blood vessels and nerves. Usually, the protruding surface of the tooth is at least partially covered with a thin, but extremely hard layer of enamel (the hardest substance in the body), which is formed by special cells - ameloblasts (adamantoblasts). The teeth of sloths and armadillos are deprived of it; on the teeth of the sea otter (sea otter) and spotted hyena, which have to regularly gnaw hard shells of mollusks or bones, its layer, on the contrary, is very thick. The tooth is fixed in a cell on the jaw with cement, which is intermediate in hardness between enamel and dentin. It may also be present within the tooth itself and on its chewing surface, for example in horses. Mammalian teeth are generally divided into four groups according to their function and location: incisors, canines, premolars (minor molars, pseudomolars, or premolars) and molars (molars). The incisors are located in the front of the mouth (on the premaxillary bones of the upper jaw and, like all teeth of the lower jaw, on the dentary bones). They have cutting edges and simple conical roots. They serve mainly to hold food and bite off parts of it. Fangs (who have them) are usually long rods pointed at the end. There are usually four of them (2 upper and lower), and they are located behind the incisors: the upper ones are in front of the maxillary bones. Fangs are used mainly for inflicting penetrating wounds in attack and defense, holding and carrying food. The premolars are located between the canines and molars. Some primitive mammals have four of them on each side of the upper and lower jaws (16 in total), but most groups have lost some of the false-rooted teeth during evolution, and in humans, for example, there are only 8 of them. The molars located at the back of the jaws, along with premolars are combined into a group of cheek teeth. Its elements may vary in size and shape depending on the nature of the feeding of the species, but usually have a wide, ribbed or tuberculate chewing surface for crushing and grinding food. In fish-eating mammals, such as toothed whales, all teeth are almost the same, approaching a simple cone in shape. They are used only to catch and hold prey, which is either swallowed whole or pre-torn into pieces, but not chewed. Some mammals, notably sloths, toothed whales, and platypuses, develop only one set of teeth throughout their lives (in the platypus, it is present only at the embryonic stage) and are called monophyodonts. However, most of the animals are diphyodont, i.e. they have two changes of teeth - the first, temporary, called milk, and permanent, characteristic of adult animals. Their incisors, canines and premolars are completely replaced once in a lifetime, and molars grow without milk predecessors, i.e. in fact, they are a late developing part of the first change of teeth. Marsupials occupy an intermediate position between monophyodonts and diphyodonts, since they retain all milk teeth, except for the changing fourth premolar. (In many of them, it corresponds to the third cheek tooth, since one premolar has been lost in the course of evolution.) Since in different types mammalian teeth are homologous, i.e. are identical in evolutionary origin (with rare exceptions, for example, in river dolphins more than a hundred teeth), each of them occupies a strictly defined position relative to the others and can be indicated by a serial number. As a result, it is not difficult to write down the set of teeth characteristic of the species in the form of a formula. Since mammals are bilaterally symmetrical animals, such a formula is compiled only for one side of the upper and lower jaws, remembering that to calculate the total number of teeth, it is necessary to multiply the corresponding numbers by two. An expanded formula (I - incisors, C - canines, P - premolars and M - molars, upper and lower jaws - numerator and denominator of a fraction) for a primitive set of six incisors, two canines, eight false-rooted and six molars is as follows:

However, an abbreviated formula is usually used, where only total number each type of teeth. For the above primitive tooth set, it looks like this:

For a domestic cow that lacks upper incisors and canines, the entry takes the following form:

and the person looks like this:

Since all types of teeth are arranged in the same order - I, C, P, M - dental formulas are often further simplified by omitting these letters. Then for a person we get:

Some teeth that perform special functions in the course of evolution can undergo very strong changes. For example, in the carnivore order (Carnivora), i.e. in cats, dogs, and the like, the upper fourth premolar (denoted P4) and lower first molar (M1) are larger than all other cheek teeth and have razor-sharp cutting edges. These teeth, called predatory teeth, are located opposite each other and act like scissors, cutting the meat into pieces that are more convenient for the animal to swallow. The P4/M1 system is a distinguishing feature of the order Carnivora, although other teeth may also perform its function. For example, the Carnivora milk set does not contain molars, and only premolars (dP3/dP4) are used as predatory ones, and in some representatives of the extinct order Creodonta, two pairs of molars, M1+2/M2+3, served the same purpose.

Skeleton. In mammals, as in all vertebrates, the skeleton consists of a large number of bones that develop independently and are interconnected by ligaments and connective tissue. In some species, it is deeply specialized, but the principle of its structure is the same for all representatives of the class. This fundamental similarity is clearly seen when comparing extreme variants, such as dolphins with a virtually absent neck, whose vertebrae are paper-thin, and giraffes with the same number, but very elongated cervical vertebrae. The skull of mammals is articulated with the vertebral column by two rounded bony protrusions in its back - the occipital condyles. For comparison, the reptilian skull has only one occipital condyle, i.e. only one point of articulation with the spine. The first two vertebrae are called the atlas and the epistrophy. Together with the next five, they make up the seven cervical vertebrae. This number is typical for all mammals, except for sloths (from six to nine) and, possibly, manatees (according to some experts - six cervical vertebrae). Then comes the largest, thoracic spine; ribs are attached to its vertebrae. This is followed by the lumbar (between the chest and pelvis) and sacral vertebrae. The latter are fused with each other and articulated with pelvic bones. The number of caudal vertebrae varies greatly depending on the type of animal and reaches several tens. In different mammals, the number of ribs surrounding many vital organs is not the same. They are usually flat and curved. Each rib is movably articulated at one end (proximal) with the dorsal vertebra, and at the other end (distal), the anterior ribs (upper in humans) are attached to the sternum with cartilage. They are called true in contrast to the back (in humans - lower), not connected to the sternum and called false. The distal end of these ribs is either attached to the cartilaginous part of the last true rib, or remains free, in which case they are called oscillating. The sternum consists of a series of more or less flattened bones fused together and is connected by cartilage to the ribs on each side. In bats, it carries a protruding keel for attaching powerful flight muscles. A similar keel on the sternum is found in flying birds and penguins (which "fly" underwater), while flightless birds like the ostrich lack it. The shoulder blade is a wide flat bone with a median ridge (awn) on the outer surface. The clavicle is connected at one end to the upper edge of the sternum, and at the other - to the shoulder process (acromion) of the spine of the scapula. The clavicle strengthens the shoulder, so it is primarily characteristic of those mammals (for example, primates) that intensively use their forelimbs for grasping. It is also present in primitive species, particularly monotremes, as it is part of the ancestral (reptilian) shoulder girdle, the skeletal formation that links the forelimb to the body axis. The clavicle has been reduced or lost in the course of the evolution of such groups of mammals that do not need it. For example, it is rudimentary in a horse, since it would only interfere with the lengthening of its stride (only a small strip surrounded by muscles remained), and it is absent in whales. The pelvis (pelvic girdle) serves to attach the hind limbs to the spine.

Limbs. The uppermost bone of the forelimb (human arm) is the humerus. It is attached to the scapula with the help of a spherical joint, and the lower end is connected with two bones of the forearm (underarm) - the radius and the ulna. The wrist usually consists of six to eight small bones (humans have eight) that connect to the bones of the metacarpus, forming the "palm" of the hand. The bones of the fingers are called phalanges. The femur of the hind limb (human leg) is articulated with a spherical joint with the pelvis. The skeleton of the lower leg consists of two bones - the tibia and the tibia. Then comes the foot, i.e. a tarsus of several bones (in humans - seven), connected to the bones of the metatarsus, to which the phalanges of the fingers are attached. The number of toes and hands depends on the type of mammal - from one to five. Five is a primitive (ancestral) state, and, for example, a horse belonging to evolutionarily advanced forms has only one finger on both the front and hind limbs (anatomically, this is a greatly enlarged middle, i.e. third, finger, and the rest are lost during specialization). The deer has functional large third and fourth fingers, forming a cloven hoof; the second and fifth are small, not reaching the ground, and the first ("big") is absent. In most mammals, the ends of the fingers are protected by claws, nails, or hooves, which are keratinized derivatives of the epidermis (the outer layer of the skin). The appearance and function of these structures vary greatly, but their general structure is the same. Mammals that rely on the entire sole when walking, i.e. on the metacarpus and metatarsus, as, for example, bears and people, are called plantigrade, moving relying only on fingers (for example, cats and dogs) are digitigrade, and hoofed forms (cow, horse, deer) are phalangeal. The body cavity of all animals is divided in two by a muscular partition called the diaphragm. In front (in humans - from above) is the chest cavity, which contains the lungs and heart, and behind (in humans - from below) - the abdominal cavity with the rest of the internal organs, except for the kidneys. Only mammals have a diaphragm: it is involved in lung ventilation. The mammalian heart is divided into four chambers - two atria and two ventricles. Each atrium communicates with a ventricle on the same side of the body, but this opening is equipped with a valve that allows blood to move in only one direction. Oxygen-depleted blood, returning to the heart from the organs of the body, enters the right atrium through large veins called hollow. It then pushes into the right ventricle, which pumps it to the lungs via the pulmonary arteries. In the lungs, the blood is saturated with oxygen and releases carbon dioxide. Oxygen-rich blood then enters the pulmonary veins, and from them into the left atrium. Then she pushes from it into the left ventricle, which pumps it through the largest artery - the aorta - to all organs of the body. The lungs are a spongy mass made up of numerous air-filled passageways and chambers surrounded by a network of capillaries. Passing through this network, the blood absorbs oxygen from the air pumped into the lungs and at the same time releases carbon dioxide into it.
Normal blood temperature in different
species of mammals is not the same, and in many bats, rodents and a number of other species it drops noticeably during sleep and seasonal hibernation. Usually close to 38°C, in the latter case it can approach the freezing point. The "warm-bloodedness" characteristic of mammals, i.e. the ability to maintain a constant body temperature is a relative concept. In many species, diurnal fluctuations in this temperature are known; in humans, for example, during the day it rises from the morning low (approx. 36.7 ° C) to about 37.5 ° C in the evening. Desert animals are exposed to intense heat every day, which also affects their body temperature; in camels, for example, it can change during the day by almost 6 ° C. And in a rodent of a naked mole rat living in relatively stable microclimatic conditions of a hole, the latter directly affect body temperature. The stomach of most mammals consists of one section, but in some species there are several, for example, four in ruminants, i.e. artiodactyl animals such as cows, deer and giraffes that chew their cud. Camels and deer are called "false-ruminants" because, although they chew the cud, they differ from the "true" ruminants in having a three-chambered stomach and some signs of teeth, legs and other organs. A number of whales have a long tubular stomach divided into several successive chambers. The lower end of the stomach opens into the small intestine, which, in turn, leads to the large intestine, which leads to the rectum. At the border between the small and large intestines digestive tract the caecum branches off. In humans and some other animals, it ends in a small rudiment - the appendix (appendix). The structure and role of the cecum varies greatly depending on the type of animal. For example, in ruminants and horses, it performs the important function of a fermentation chamber for the digestion of plant fibers and is exceptionally long, while in other mammals it is relatively small, although it takes an active part in digestion. The mammary glands produce milk to feed the young. These structures are laid in representatives of both sexes, but in males they are underdeveloped. In all mammals, except for the platypus and other monotremes, the ducts of the mammary glands open on fleshy outgrowths - nipples, which the cubs capture by mouth when feeding. In some species, such as cows, the ducts of the mammary gland first flow into a chamber called a cistern, where milk accumulates, which then flows out through long tubular nipples. Single-pass nipples do not, and the milk ducts open as porous holes in the skin.
NERVOUS SYSTEM
The nervous system functions as an integral whole with the sense organs, such as the eyes, and is controlled in mammals by the brain. The most large part the latter is called the cerebral hemispheres (in the occipital region of the skull there are two smaller hemispheres of the cerebellum). The brain is connected to the spinal cord. In all mammals, with the exception of monotremes and marsupials, unlike other vertebrates, the right and left cerebral hemispheres are interconnected by a compact bundle of nerve fibers called the corpus callosum. There is no corpus callosum in the brain of monotremes and marsupials, but the corresponding areas of the hemispheres are also connected by nerve bundles; for example, the anterior commissure connects the right and left olfactory regions with each other. The spinal cord - the main nerve trunk of the body - passes through a canal formed by the openings of the vertebrae and stretches from the brain to the lumbar or sacral spine, depending on the type of animal. From each side of the spinal cord, nerves depart symmetrically to different parts of the body. Touch in general terms is provided by certain nerve fibers, the innumerable endings of which are located in the skin. This system is usually supplemented by hairs that act as levers to press on nerve-riddled areas. Vision is more or less developed in all mammals, although some mole rats have small, underdeveloped eyes covered with skin and are hardly even capable of distinguishing light from darkness. The animal sees the light reflected from objects, absorbed by the eye, which transmits the appropriate signals to the brain for recognition. In other words, the eyes themselves do not "see", but only act as transducers of light energy. One of the problems of obtaining a clear visual image is overcoming chromatic aberration, i.e. a fuzzy colored border that appears at the edges of an image formed by a simple lens (a non-composite transparent object with two opposite surfaces, of which at least one is curved). Chromatic aberration is an inherent property of the lens of the eye and occurs because, like a simple lens, it refracts shorter wavelength light (such as violet) more strongly than long wavelength light (such as red). Thus, the rays of all wavelengths are not focused at one point, giving a clear image, but some are closer, others are farther, and the image is blurry. In a mechanical system such as a camera, chromatic aberration is corrected by gluing lenses with different mutually compensating refractive powers. The mammalian eye solves this problem by "cutting off" most of the shortwave light. The yellowish lens acts as a yellow filter: it absorbs almost all ultraviolet (which is partly why a person does not perceive it) and part of the blue-violet part of the spectrum. Not all of the light that enters the pupil and reaches the light-sensitive retina is used for vision. Some of it passes through the retina and is absorbed by the underlying pigment layer. For nocturnal animals, this would mean too much loss of the small amount of available light, so in many such species the bottom of the eye is mirrored: it reflects unused light back to the retina for additional stimulation of its receptors. It is this reflected light that causes the eyes of some mammals to "glow" in the dark. The mirror layer is called the tapetum lucidum (mirror). Mammals have two main types of areolet. The first is fibrous, characteristic of ungulates. Their areolet mainly consists of a shiny layer of connective tissue fibers. The second type is cellular, for example, in carnivores. In this case, it consists of several layers of flattened cells containing fibrous crystals. The mirror is usually located in the choroid behind the retina, but, for example, in some bats and in the Virginia opossum it is embedded in the retina itself. The color that the eyes shine with depends on the amount of blood in the capillaries of the choroid and the content of rhodopsin (purple light-sensitive pigment) in the rod-shaped elements of the retina through which the reflected light passes. Despite the widespread belief that color vision is uncommon in mammals, most of which supposedly see only shades of gray, evidence is accumulating that many species, including domestic cats and dogs, do, at least to some extent, see colors. Color vision is probably most developed in primates, but is also known in the horse, giraffe, opossum, several species of squirrels, and many other animals. Hearing is well developed in many mammals, and for 20% of their species, it largely replaces vision. The hearing aid consists of three main parts. Mammals are the only group of animals with a well-developed outer ear. The auricle picks up sound waves and sends them to the eardrum. On the inner side of it is the next section - the middle ear, an air-filled chamber with three bones (hammer, anvil and stirrup), which mechanically transmit vibrations from the eardrum to the inner ear. It includes the cochlea, a spirally coiled, fluid-filled tube with hair-like outgrowths inside. Sound waves cause fluid vibrations and, indirectly, the movement of hairs, which serves as a stimulation of nerve cells at their base. The frequency range of perceived sounds depends on the type of animal. Many small mammals hear "ultrasound" at frequencies that are too high for human hearing. Ultrasound is especially important for species that use echolocation - the capture of reflected sound waves (echoes) to recognize objects in the environment. This way of orientation is typical for bats and toothed whales. On the other hand, many large mammals can pick up low-frequency "infrasound" that humans also cannot hear. The sense of smell is associated with thin sensory membranes (olfactory mucosa) at the back of the nasal cavity. They capture the molecules of odorous substances present in the inhaled air. The olfactory mucosa consists of nerve and supporting cells covered with a layer of mucus. The endings of its nerve cells carry bundles of olfactory "cilia" up to 20 in number, which together form a kind of fleecy carpet. Cilia serve as odor receptors, and the density of their "carpet" depends on the type of animal. In a person, for example, there are up to 20 million of them on an area of ​​5 cm2, and in a dog - more than 200 million. Odorous molecules dissolve in mucus and fall into special sensitive pits on the cilia, stimulating nerve cells, which send impulses to the brain for analysis and recognition.
COMMUNICATION
Sound. Mammals use sounds to communicate, such as alarms, threats, or calls to mate (some animals, particularly certain species of deer, only speak during the breeding season). A number of species, including rabbits, have well-developed vocal cords but use them only when under extreme stress. Non-vocal sound communication is known in many mammals: rabbits, for example, knock on the ground with their paws, white-footed hamsters drum with their front paws on hollow objects, and male deer crack their horns on branches. Sound communication plays an important role in the social interactions of animals, since in general they can express all basic emotions with sounds. Bats and toothed whales make sounds for echolocation, allowing them to navigate in the dark or in murky water, where vision would be clearly insufficient for this.
Visual. Mammals communicate with more than just sounds. For example, in some species, the white underside of the tail, if necessary, is shown to relatives as a visual signal. The "stockings" and "masks" of certain antelopes are also widely used to display their condition. A particular example of visual communication is seen in the American pronghorn, which sends messages to other members of its species within a 6.5 km radius using a patch of long white hair on the rump. The frightened animal fluffs up these hairs, which seem to flare up in the sunlight, becoming clearly visible at a great distance.
Chemical. Odors, which are determined by various chemicals in urine, feces, and glandular secretions, are widely used by mammals in social interactions, for example, to mark territory or recognize suitable mating partners. In the latter case, the smell makes it possible not only to distinguish males from females, but also to determine the stage of the reproductive cycle of a particular individual. Chemical signals used for intraspecific communication are called pheromones (from the Greek pherein - to carry and hormon - to excite, i.e. pheromones "transfer excitement" from one individual to another). They are divided into two functional types: signaling and motivating. Signal pheromones (releasers) cause specific behavioral responses of another animal, for example, they attract individuals of the opposite sex, make them follow an odorous trail, flee, or attack an enemy. Motivating pheromones (primers) lead to physiological changes in relatives. For example, the achievement of sexual maturity in house mice is accelerated by the smell of substances contained in the urine of adult males, and slowed down by pheromones in the urine of adult females.
See also ANIMAL COMMUNICATION.
BREEDING
Fish and amphibians usually lay their eggs (eggs) in the water. Their eggs are equipped with membranes that help the developing embryos shed waste and absorb nutrients, primarily from the calorie-rich yolk. The yolk sac and other membranes of this type are located outside the embryo, therefore they are called extraembryonic membranes. Reptiles were the first vertebrates to acquire three additional extra-embryonic membranes, allowing them to lay eggs on land and ensure development without an aquatic environment. These shells made it possible for the embryo to receive nutrients, water and oxygen, as well as to excrete metabolic products, being in a non-aqueous environment. The innermost of them - the amnion - forms a bag filled with a brackish liquid. It surrounds the embryo, providing it with a liquid environment similar to that in which the embryos of fish and amphibians are immersed in water, and the animals that possess it are called amniotes. The outermost shell - the chorion - together with the middle one (allantois) performs other important functions. The shell surrounding the fish egg is also called the chorion, but this structure in them is functionally comparable to the so-called. the shiny shell (zona pellucida) of a mammalian egg, which is present even before its fertilization. Animals inherited extraembryonic membranes from reptiles. In oviparous monotremes, these membranes still perform their ancestral functions, since the energy needs of the embryo are met by the rich reserves of yolk in large eggs covered with shell. In marsupial and placental embryos, which receive most of the energy necessary for development from the mother, the eggs contain little yolk, and the embryo soon attaches to the wall of the uterus with the help of outgrowths of the chorion penetrating into it. In most marsupials and some placentals, it fuses with the yolk sac to form a primitive placenta called the yolk. The placenta (also called the placenta or placenta) is a formation that provides a two-way exchange of substances between the embryo and the mother's body. Through it, nutrients enter the embryo, its respiration and removal of metabolic products. Most placental mammals the chorion forms it together with the allantois, and it is called the allantoid. The duration of the period from fertilization of the egg to the birth of the cub varies from 12 days in some marsupials to about 22 months in the African elephant. The number of newborns in a litter usually does not exceed the number of nipples in the mother and, as a rule, is less than 14. However, in some mammals, litters are very large, for example, a Madagascar tenrec female from the order of insectivores with 12 pairs of mammary glands sometimes gives birth to more than 25 cubs. Usually one embryo develops from a fertilized egg, but polyembryony is also found, i.e. it gives rise to several embryos that separate at the earliest stages of development. Occasionally, this occurs in many species, including completely identical identical twins in humans, but in the nine-banded armadillo, polyembryony is a common occurrence, and the litter, as a rule, consists of "quadruplets". In marsupials, young are born underdeveloped and complete development in the mother's pouch. See also marsupials. Immediately after birth (or, in the case of monotremes, after hatching from eggs), mammals feed on mother's milk. The mammary glands are usually arranged in pairs, which range from one (for example, in primates) to 12, as in tenrecs. At the same time, many marsupials have an odd number of mammary glands and only one nipple is developed in the middle of the abdomen.

KOALA takes care of her "bear" for almost four years.

locomotion
In general, the mechanism of movement (locomotion) is the same in all mammals, but its specific methods developed in many divergent directions. When the animals' ancestors first crawled onto land, their fore and hind limbs were short and widely spaced, making movement on land slow and clumsy. The evolution of mammalian locomotion has been directed mainly towards increasing speed by lengthening and straightening the legs and lifting the torso off the ground. This process required certain changes in the skeleton, including the loss of a number of elements of the reptilian shoulder girdle. Due to the diversity of specialization, the animals have mastered all possible ecological niches. In modern mammals, modes of locomotion include digging, walking, running, jumping, climbing, gliding, flapping flight, and swimming. Burrowing forms such as moles and gophers move below the soil surface. The powerful forelimbs of these mammals are pushed forward so that the paws can work in front of the head, and the shoulder muscles are very strongly developed. At the same time, their hind limbs are weak and unspecialized. The brushes of such animals can be very large, adapted for raking soft soil, or armed with powerful claws for "drilling" hard ground. Many other mammals dig holes in the ground, but digging, strictly speaking, does not apply to their methods of locomotion.

Many small species, such as rats, mice and shrews, are characterized by a relatively massive body with short limbs and usually move in dashes. It is hardly worth talking about some kind of their locomotor specialization. Some mammals, such as bears, are best suited for walking. They belong to the plantigrade type and rely on the feet and palms when walking. If necessary, they can switch to hard running, but they do it clumsily and cannot maintain high speed for a long time. Very large animals are also adapted for walking, such as elephants, in which there is a tendency to elongate and strengthen the upper leg bones while shortening and expanding the lower ones. This turns the limbs into massive columns supporting the enormous mass of the body. Conversely, in fast-running animals such as horses and deer, the lower segments of the legs are rod-shaped, capable of moving quickly back and forth. At the same time, the muscles of the limbs are concentrated in their upper part, leaving mainly powerful tendons below, sliding, as if in blocks, along the smooth surfaces of the cartilage and stretching to the places of attachment to the bones of the feet and hands. Additional adaptations for fast running include the reduction or loss of the outer fingers and the convergence of the remaining ones. The need to catch up with agile prey and to cover long distances in the shortest possible time, searching for it, led to the appearance in cats and dogs of another method of locomotion - on the fingers. At the same time, the metacarpus and metatarsus lengthened, which made it possible to increase the speed of running. Her record for mammals is recorded in cheetahs: approximately 112 km / h. Another main direction in the evolution of rapid movement on the ground was the development of the ability to jump. Most animals, whose life is in direct proportion to the speed of their locomotion, move forward using mainly the pushes of their hind legs. The extreme development of this mode of movement, combined with a change in lifestyle, has led to profound structural transformations of jumping species. Their main morphological change was the elongation of the hind limbs, primarily their lower parts, which led to an increase in the push and the ability to soften the blow upon landing. To provide the strength needed for long successive jumps, the muscles of these limbs have grown strongly in the transverse direction. At the same time, their outer fingers were reduced or disappeared altogether. The limbs themselves spread widely to increase stability, and the animal as a whole became digitigrade. In most cases, the forelimbs have greatly decreased, and the neck has shortened. The tail of such species is very long, like a jerboa, or relatively short and thick, like a kangaroo. It serves as a balancer and to some extent as a steering device. The hopping method of locomotion allows you to achieve maximum acceleration. Calculations show that the longest jump is possible at a take-off angle of 40-44°. Rabbits use a mode of movement intermediate between running and jumping: powerful hind legs push the body forward, but the animal lands on its front legs and is ready to repeat the jump, only once again grouped in its original position. In order to lengthen the jumps and thus cover the distance more efficiently, some animals have acquired a parachute-like membrane that stretches along the body between the fore and hind limbs and is attached to the wrists and ankles. When spreading the limbs, it straightens out and provides sufficient lift for planning from top to bottom between branches located at different heights. The rodent American flying squirrel is a typical example of animals moving in this way. Similar gliding webs have independently evolved in other groups, including the African spinytail and the Australian glider (flying possum). The animal can start flying from almost any position. With its head extended forward, it glides through the air, picking up speed under the force of gravity, sufficient to turn the body upward before landing, so that it comes at her in an upright position. After that, the animal is ready to climb up the tree trunk and, having climbed to the required height, repeat the flight. Among mammals, the kaguans, or woolly wings, living in the Far East and the Philippine Islands, have the most perfect adaptation for planning. Their lateral membrane continues along the neck and tail, reaches the thumbs and connects the other four. The bones of the limbs are long and thin, which ensures maximum stretching of the membrane when the limbs are extended. With the exception of such gliding, which has evolved as a special type of locomotion, no transitions from ground to flapping flight have been observed in modern mammals. The only mammals that can actually fly are bats. The oldest known fossil representatives already had well-developed wings, the structure of which has hardly changed over 60 million years. These flying mammals are thought to have descended from some primitive group of insectivores. The forelimbs of bats are modified into wings. Their most notable feature is the strong elongation of the four fingers, with a flying web between them. However, the thumb extends beyond its front edge and is usually armed with a hook-shaped claw. The long bones of the limbs and their major joints have undergone significant changes. The humerus is distinguished by large outgrowths (skewers) to which muscles are attached. In some species, the skewers are long enough to form a secondary articulation with the scapula, which gives the shoulder joint unusual strength, but limits movement in it to one plane. The elbow joint is formed almost exclusively by the humerus and radius, and the ulna is reduced and practically non-functional. The flying membrane usually stretches between the ends of the 2nd-5th fingers and further along the sides of the body, reaching the legs at the feet or ankles. In some species, it continues between the legs from ankle to ankle, surrounding the tail. At the same time, a cartilaginous process (spur) departs from the inside of the ankle joint, which supports the back membrane. The nature of the flight of bats of different genera and species is not the same. Some of them, such as bats, flap their wings measuredly. Folded lips fly very fast, and the flight speed of, for example, bagpipes can change dramatically. Some fly as smoothly as night butterflies. Be that as it may, flight is the main mode of locomotion in bats, and it is known that some migratory species cover up to several hundred kilometers without rest. At least one representative of almost every order of mammals swims well. In fact, all animals, even bats, can, if necessary, stay on the water. Sloths move even faster in it than on land, and some rabbits have mastered this environment as well as muskrats. There are various levels of special adaptation of mammals to life in the water. For example, the mink does not have any special adaptations for this, with the exception of greased fur, and whales in body shape and behavior resemble fish rather than animals. In semi-aquatic forms, the hind feet are usually enlarged and provided with a web between the fingers or a fringe of coarse hair, like an otter. Their tail can be modified into a paddle or rudder, becoming flattened vertically like a muskrat or horizontally like a beaver. Sea lions have adapted to life in the water even better: their front and hind legs are extended and turned into flippers (the upper segments of the limbs are immersed in the fat layer of the body). At the same time, they still retain thick fur to keep them warm and are able to walk on land on all fours. Real seals went further along the path of specialization. For swimming, they use only their hind limbs, which can no longer turn forward to move on land, and thermal insulation is provided mainly by a layer of subcutaneous fat (blubber). Complete adaptation to life in the water is demonstrated by cetaceans and sirens. It is accompanied by profound morphological changes, including the complete disappearance of the external hind limbs, the acquisition of a streamlined, fish-like body shape, and the disappearance of the hairline. To keep whales warm, like real seals, a thick layer of blubber helps, surrounding the body. Translational movement in the water is provided by horizontal fins with a cartilaginous frame located at the back of the tail.
SELF PRESERVATION
All mammals have evolved certain mechanisms of self-preservation, and many have acquired special protective adaptations in the course of evolution.

The African Crested Porcupine is protected by a mane ("comb") of flexible spikes and sharp needles. Spreading them, he turns to the enemy with his tail and makes a sharp movement back, trying to prick the aggressor.

Protective covers. Some animals, such as a hedgehog, are covered with needles and, in case of danger, curl up into a ball, exposing them in all directions. A similar method of protection is used by armadillos, which are able to completely fence themselves off from the outside world with a horny shell, which also protects the body from the sharp spines of cacti, which are the most common vegetation in the habitats of these animals. The North American porcupine went even further in the development of protective covers. It is not only covered with jagged needles, which, stuck in the body of the enemy, can lead to his death, but also very deftly wields a prickly tail, inflicting quick and accurate blows on the enemy.
glands. Mammals use for protection and chemical weapon. This method is most mastered by the skunk, which produces a caustic and very smelly liquid in the paired anal glands at the base of the tail. By contracting the muscles surrounding the glands, it can throw its thin jet at a distance of up to 3 m, aiming at the enemy's most vulnerable spots - the eyes, nose and mouth. Keratin is an important component of the outer layer of the skin (epidermis) of mammals. It is a strong, elastic and water-insoluble protein. It is essential for the protection of animals, since it protects the underlying tissues from chemical irritants, moisture and mechanical damage. Areas of the skin that are particularly susceptible to aggressive action external environment, are protected by a thickened epidermis with an increased content of keratin. An example is calloused growths on the soles. Claws, nails, hooves and horns are all specialized keratin formations. Claws, nails and hooves consist of the same structural elements, but differ in their location and degree of development. The claw consists of two parts - the upper plate, called the claw, and the lower plantar. In reptiles, they usually form two halves of a conical cap enclosing the fleshy end of the finger. In the claws of mammals, the lower plate is reduced and practically does not cover the finger. The upper plate of the nail is wide and flat, and the narrow remnant of the lower one is hidden between its edge and the fingertip. In the hoof, both plates are enlarged, thickened and curved, with the upper one (hoof wall) surrounding the lower one (its sole). The fleshy end of the finger, called the arrow in horses, is thus pushed back and up. Claws are used primarily for digging, climbing and attacking. The beaver combs the fur with a forked claw of the hind paw. Cats usually keep their claws retracted into special cases so as not to dull their ends. Deer often defend themselves with ax-sharp hooves and can kill snakes with them. The horse is famous for its powerful kick of the hind legs, and is able to kick with each leg individually and both at once. Defensively, it can also rear up and sharply strike the enemy from top to bottom with its front hooves.
Horns. In the process of evolution, mammals very early acquired outgrowths of the skull used as weapons. Some species had them already in the Eocene (about 50 million years ago) and have since become more and more characteristic of many ungulates. In the Pleistocene (began about 1.6 million years ago), these outgrowths reached fantastic sizes. In many cases, they are more important for fights with relatives, for example, when males compete for a female, than as a means of protection from predators. In principle, all horns are solid outgrowths on the head. However, they developed and specialized in two different directions. One type can be called true horns. They consist of a usually unbranched bone core extending from the frontal bones, covered with a sheath of hard keratinized horny tissue. This hollow sheath removed from the cranial outgrowths is used to make various "horns" into which they blow, pour wine, etc. True horns are usually present in animals of both sexes and are not shed during their entire lives. The exception is the horns of the American pronghorn. Their horny, like in real horns, not only bears a small process (sometimes more than one), forming a "fork", but is shed (replaced) every year. The second type is the antlers of deer, which, in their fully developed form, consist only of bone without a horn covering, i.e. actually "horns" they are called incorrectly. These are also processes of the frontal bones of the skull, usually branched. Deer-type antlers are present only in males, although here the caribou (reindeer) is an exception. Unlike real ones, these horns are shed every year and grow back. Rhino horn is also not real: it consists of hardened keratinized fibers (“hair”) glued together. Giraffe horns are not horny structures, but bone processes covered with skin and with normal hair. Real horns are characteristic of the group of bovids - cattle, sheep, goats and antelopes. In wild buffalo-like mammals, they are often strongly thickened at the base and form, as it were, a helmet, for example, in the musk ox and black African buffalo. In most types of cattle, they are only slightly curved. The ends of the horns of all species point upwards to some extent, which increases their effectiveness as a weapon. The horns of the bighorn sheep are the heaviest and largest in relation to the overall size of the animal. In males, they are massive and twisted into a spiral that changes its shape during growth, so that their ends can eventually describe more than one full circle. In combat, these horns are used as a battering ram rather than as a stabbing weapon. In females, they are smaller and almost straight. The horns of wild goats specialized differently. The length gives them an impression. Arcuate, widely diverging in the mountain goat and straight, twisted with a corkscrew in the markhor goat, they are very different from sheep, which, even with a greater overall length, seem smaller, since their ends are closer to the base due to the spiral bend. Horns appear at an early stage in the development of an individual. In very young animals, their rudiments are loosely attached to the frontal bones, can be separated from the skull, and even more or less successfully transplanted onto the head of another animal. The practice of transplanting horns originated in India or the Far East, and may be related to the origin of the legends about unicorns.
Teeth. In most hornless mammals, the main weapon is the teeth. However, some species, such as anteaters, are deprived of them, and, say, rabbits with perfectly developed teeth, never use them for protection, no matter how great the danger. Most rodents put their chisels to good use when threatened. Bats can bite, but in most cases their teeth are too small to inflict serious wounds. Predators use in battle mainly sharp, long fangs, which are vital to them. Cat fangs are dangerous, but the bite of dogs is more powerful, because in a duel these animals are not able to help themselves with their claws. Some mammals have evolved highly specialized teeth called tusks. They are used primarily for food, but can also serve as weapons. Most wild pigs, such as the European wild boar, dig up edible roots with their long tusks, but they can also inflict a serious wound on the enemy with these teeth. The tusks of the walrus are used to rip up the seabed in search of bivalves. They are well developed in both sexes, although the females are usually thinner. Such a tooth can reach a length of 96 cm with a mass of more than 5 kg. The narwhal is the only cetacean with a tusk. It is usually developed only in males and arises from the left side of the upper jaw. It is a forward-protruding straight, spirally twisted rod that can exceed 2.7 m in length and weigh more than 9 kg. Since it is normally present only in males, one of its uses is probably in fights for females. African elephants- owners of the largest tusks among living mammals. They use them in combat, for digging and marking territory. A pair of such tusks can reach a total length of 3 m, yielding over 140 kg of ivory.
AGGRESSIVE BEHAVIOR
According to the aggressive behavior of mammals, mammals can be divided into three main groups: harmless (never attacking warm-blooded animals for the purpose of killing), indifferent (capable of provoked attack and killing), and aggressive (killing regularly).
Harmless. Rabbits are perhaps the most harmless of all mammals: they do not even try to pretend that they are fighting, no matter how desperate their situation may be. Rodents are generally harmless, although some species, such as the American red squirrel, can kill and eat a small animal on occasion. The blue whale is the largest and strongest mammal that has ever lived, but it feeds on small crustaceans and fish, thus being among the most harmless creatures.
Indifferent. Large herbivores fall into this category, which are aware of their strength and can attack in case of provocation or danger threatening the young. Male deer are harmless for nine months of the year, but become extremely unpredictable and dangerous during the rutting season. In a group of cattle, the bulls are ready to fight at any time. The fact that the red color infuriates them is a delusion: the bull attacks any object moving in front of its nose, even white. An Indian buffalo may attack a tiger without provocation, perhaps following the instinct to protect its young. An injured or cornered African buffalo is considered one of the most dangerous animals. Elephants, except for individual evil individuals, are harmless outside the mating period. Oddly enough, the passion for killing can develop in donkeys, and it acquires in them the character of a purely sports passion. For example, on the island of Mona off the coast of Puerto Rico lived a donkey that spent free time hunting wild pigs.
Aggressive. Representatives of the order of carnivores belong to typical aggressive animals. They kill to get food, and normally do not go beyond purely nutritional needs. However, a dog that loves to hunt can kill more game than it can eat at one time. Weasel tends to strangle all the mice in the colony or chickens in the chicken coop and only then take a "break for lunch". The shrew, for all its small size, is extremely pugnacious and is capable of killing a mouse twice its size. Among cetaceans, the killer whale is not without reason called the killer whale. This marine predator can attack literally any animal it encounters. Killer whales are the only whales that regularly feed on other warm-blooded whales. Even huge smooth whales, faced with a flock of these killers, take flight.
SPREAD
Distribution areas (ranges) certain types mammals are extremely diverse and are determined both by climatic conditions and by the isolation from each other of large land masses caused by tectonic processes and continental drift.
North America. Since the isthmus between North America and Eurasia disappeared relatively recently (rising sea levels flooded the land bridge on the site of the Bering Strait that existed 35,000-20,000 years ago), and both regions are located in the Northern Hemisphere, between their faunas, including mammals, there is great similarity. Typical animals include moose, reindeer and red deer, mountain sheep, wolves, bears, foxes, wolverines, lynxes, beavers, marmots, hares. in Eurasia and North America live large bulls (bison and bison, respectively) and tapirs. However, only in North America are species such as pronghorn and bighorn goat, puma, jaguar, black-tailed and white-tailed (Virginian) deer and gray fox.
South America. This continent is very peculiar in terms of the fauna of mammals, although many forms migrated from here through the Isthmus of Panama to North America. One of the features of many local tree animals is the presence of a tenacious tail. Only in South America do rodents of the guinea pig family (Caviidae) live, including, in particular, the Patagonian mara, which looks more like a hare than a species close to it - a guinea pig. The capybara is also found here - the largest modern rodent, reaching a mass of 79 kg. Guanaco, vicuña, alpaca and llama, characteristic only of the Andes, are South American representatives of the camelid family (Camelidae). Anteaters, armadillos and sloths come from South America. There are no local species of cattle and horses, but there are many deer and a species of bears - spectacled. Pig-like forms are represented by peculiar bakers. Opossums, some felines (including the jaguar and puma), canines (including the large red wolf), rabbits and broad-nosed monkeys (which differ from the Old World species in a number of significant features) are found here, squirrels are well represented. The mammals of Central America are mostly of South American origin, although some species, such as large climbing hamsters, are unique to this region.
Asia. Large mammals are particularly diverse in Asia, including elephants, rhinos, tapirs, horses, deer, antelopes, wild bulls, goats, rams, pigs, felines, canines, bears, and primates, including gibbons and orangutans.
Europe. In terms of fauna, Europe is part of Eurasia, but large mammals are almost extinct here. Deer and fallow deer are still found in protected forests, and wild boars and chamois still live in the Pyrenees, the Alps and the Carpathians. Mouflon - supposedly a close relative of domestic sheep - is known in Sardinia and Corsica. The wild bison virtually disappeared from Europe during World War II. Of the small mammals in limited quantities, for example, the otter, badger, fox, forest cat, ferret, weasel are still preserved; squirrels and other rodents, hares and rabbits are quite common.
Africa. A very spectacular mammalian fauna still inhabits Africa, where antelopes are especially diverse. Zebras still form large herds; there are many elephants, hippos and rhinos. Most of the mammal groups are represented in Africa, although such northern forms as deer, rams, goats and bears are either absent or very few in number. The giraffe, okapi, African buffalo, aardvark, gorilla, chimpanzee and warthog are unique to this continent. Most "African" lemurs live on the island of Madagascar.
Australia. The Australian region for a long time (perhaps at least 60 million years) was isolated from the rest of the continents and, of course, differs strikingly from them in terms of the fauna of mammals. Animals characteristic of this region are monotremes (echidna, prochidna and platypus) and marsupials (kangaroos, bandicoots, possums, koalas, wombats, etc.). The wild dingo dog appeared in Australia relatively recently: it was probably brought here by primitive people. Local rodents and bats are found here, but there are no wild ungulates. Distribution by climatic zones. The habitats of wild animals are largely determined by climate. The Arctic and Subarctic are characterized by musk ox, caribou, polar bear, walrus and lemmings. The northern temperate regions are home to most deer, bears, rams, goats, bison, and horses. Cats and dogs also have a northern origin, but they have spread almost all over the world. Antelopes, tapirs, zebras, elephants, rhinos, feral pigs, peccaries, hippos and primates are typical of the tropics. The southern temperate regions are small in area and are characterized by only a few specialized forms.
CLASSIFICATION
The class of mammals (Mammalia) is divided into two subclasses - the first animals (Prototheria), i.e. monotremes, or oviparous, and real animals (Theria), which include all other modern orders. Marsupials and placental mammals have much in common and origin closer friend to each other than each of these groups - to single-pass. All these animals are viviparous and have a simplified shoulder girdle that is not rigidly attached to the axial skeleton. The subclass is divided into two modern infraclasses - Metatheria (lower animals, i.e. marsupials) and Eutheria (higher animals, i.e. placentals). In the latter, babies are born at relatively late stages of development, the placenta is allantoid type, the teeth and general structure are usually highly specialized, and the brain, as a rule, is rather complex. The orders of living mammals are listed below. SUBCLASS PROTOTHERIA - FIRST BEASTS
Order Monotremata (single pass) includes two families - platypuses (Ornithorhynchidae) and echidnas (Tachyglossidae). These animals reproduce in the same way as their reptilian ancestors, i.e. laying eggs. They combine the characteristics of mammals (wool, mammary glands, three ear bones, diaphragm, warm-bloodedness) with some features of reptiles, for example, the presence of a coracoid (a bone that strengthens the shoulder between the shoulder blade and the sternum) in the shoulder girdle. Modern monotremes are common only in New Guinea and Australia, but the remains of a fossil platypus 63 million years old have been found in Patagonia (South America). Echidnas lead a terrestrial lifestyle and feed on ants and termites, while the platypus is a semi-aquatic animal that eats earthworms and crustaceans.
INFRACLASS METATHERIA - LOWER Beasts
Marsupials have long been attributed to a single order Marsupialia, however, modern studies have shown that within this group there are seven distinct evolutionary lines, which are sometimes distinguished as independent orders. In some classifications, the term "marsupials" refers to the infraclass as a whole, the name of which has been changed from Metatheria to Marsupialia. The order Didelphimorphia (American opossums) includes the most ancient and least specialized marsupials, probably originating in North America in the middle of the Cretaceous, i.e. almost 90 million years ago. Modern forms, such as the Virginia opossum, are promiscuous and live in a wide variety of conditions. Most of them are omnivorous (some eat mainly fruits or insects) and inhabit tropical latitudes from southern Mexico to northern Argentina (some reach Canada and Chile). A few species carry their young in a pouch, but most do not. The order Paucituberculata (small tuberculate) was the richest in forms in the Tertiary period (about 65-2 million years ago), but now it is represented by only one family Caenolestidae, the species of which are devoid of a real bag. Caenoles are small animals living on the ground, feeding exclusively on insects and living in the temperate forests of the South American Andes. The Microbiotheria order is represented by the only living species, the Chilean opossum from the Microbiotheriidae family, limited in its distribution by the southern beech (notophagus) forests of southern Chile and Argentina. Its relationship with the rest of the marsupials of the New World and Australia, as well as placental mammals, is completely unclear. This is small animal with a real bag, feeding on insects and building nests on branches in the bamboo undergrowth. The order Dasyuromorphia (predatory marsupials) includes the least specialized Australian marsupials and consists of three families, two of which have only one species. Talitsin, or Tasmanian wolf, from the family of marsupial wolves (Thylacinidae) is a large predator that used to live in Tasmania. The nambat, or marsupial anteater (family Myrmecobiidae), feeds on ants and termites and lives in woodlands in southern Australia. The Dasyuridae family, which includes marsupial mice, marsupial rats, marsupial martens and marsupial (Tasmanian) devil, unites wide range insectivorous and predatory forms inhabiting New Guinea, Australia and Tasmania. All of them are devoid of a bag. The order Peramelemorphia (bandicoots) includes the families of bandicoots (Peramelidae) and rabbit bandicoots (Thylacomyidae). These are the only marsupials that have acquired a chorioallantoic placenta, which, however, does not form the fingerlike villi that characterize the placenta of the same type in higher animals. These small or medium-sized animals with an elongated snout move on four legs and feed mainly on insects and other small animals. They live in Australia and New Zealand. The order Notoryctemorphia (marsupial moles) includes a single representative, the marsupial mole (family Notoryctidae), which resembles real moles in size and body proportions. This insectivorous animal inhabits the sand dunes of the interior of Australia and literally swims in the thickness of the sand, which is facilitated by the large claws of its forelimbs and a hard leathery shield on the nose. The order Diprotodontia unites most of the mammals characteristic of Australia. The families of koalas (Phascolarctidae), wombats (Vombatidae), climbing marsupials (Phalangeridae), marsupial flying squirrels (Petauridae) and kangaroos (Macropodidae) include mainly herbivorous forms, while pygmy possums (Burramyidae) and some marsupial flying squirrels prefer insects, and possums Honey badgers (Tarsipedidae) specialize in pollen and nectar. SUBCLASS THERIA - REAL Beasts.
INFRACLASS EUTHERIA - HIGHER Beasts
As already noted, the higher animals are placental mammals. The order Xenarthra (semi-toothed), formerly called Edentata, is one of the most recent placental evolutionary lineages. It radiated during the Tertiary period (65 - about 2 million years ago) in South America, occupying very peculiar ecological niches. Anteaters (Myrmecophagidae), herbivorous sloths (families Megalonychidae and Bradypodiidae), and mainly insectivorous armadillos (Dasypodidae), which specialize in feeding on ants and termites, belong to the edentulous. In these animals, the spine is strengthened in a special way (vertebrae with additional joints), the skin is reinforced with bone shields or additional layers of connective tissue, and the teeth are without enamel and roots. The distribution of the group is mainly limited to the New World tropics; only armadillos penetrated the temperate zone.

The order Insectivora (insectivora) now occupies the ecological niches of the oldest Mesozoic mammals. In most cases, these are small land nocturnal animals that feed on insects, other arthropods and various soil invertebrates. Their eyes, as a rule, are quite small, as are the visual regions of the brain, the hemispheres of which are poorly developed and do not cover the cerebellum. At the same time, the olfactory lobes, responsible for the perception of smells, are longer than the rest of the brain. Systematists are still arguing about the number of families in this order, but six are most often distinguished (for modern species). Shrews (Soricidae) are extremely small mammals; in some of them the metabolic rate reaches the highest level known to animals. Other insectivorous families are moles (Talpidae), golden moles (Chrysochloridae), hedgehogs (Erinaceidae), tenrecs (Tenrecidae) and slittooths (Solenodontidae). Representatives of the detachment live on all continents except Australia and Antarctica. The order Scandentia (tupai) with one family of the same name was not singled out for a long time as a separate group, referring its representatives to primitive primates, to which they are really closely related, as well as to bats and woolly wings. Tupai are similar in size and appearance to squirrels, live only in the forests of East Asia and feed mainly on fruits and insects. The order Dermoptera (woolly wings) includes only two species, also called kaguans. They inhabit the rainforests of Southeast Asia and are characterized by a broad gliding web that extends from their neck to the fingertips of all four limbs and the end of their tail. The ridge-like, serrated lower incisors are used as scrapers, and the diet of coleopterans consists mainly of fruits, buds, and leaves. The order Chiroptera (bats) is the only group of mammals capable of active flight. By diversity, i.e. number of species, it is second only to rodents. The order includes two suborders: fruit bats (Megachiroptera) with one family of fruit bats (Pteropodidae), uniting fruit-eating bats of the Old World, and bats (Microchiroptera), modern representatives of which are usually divided into 17 families. Fruit bats navigate mainly by sight, while bats make extensive use of echolocation. The latter are distributed throughout the world, most of them catch insects, but some are specialized in feeding on fruits, nectar, terrestrial vertebrates, fish, or bloodsucking. The order Primates (primates) includes humans, monkeys and prosimians. Primates have free-rotating arms at the shoulders, well-developed clavicles, usually opposing thumbs (a climbing aid), one pair of mammary glands, and a well-developed brain. The semi-monkey suborder includes the bat, lemurs and lorises, galagos from the African continent, tarsiers from the East Indies and the Philippines, etc. living mainly in Madagascar. broad-nosed monkeys living in the New World include howler monkeys, capuchins, squirrel monkeys (saimiri), spider monkeys (coats), marmosets, etc. The group of narrow-nosed monkeys of the Old World includes monkeys (macaques, mangabeys, baboons, thin-bodied, proboscis, etc.), anthropoids (gibbons from Southeast Asia, gorillas and chimpanzees from equatorial Africa and orangutans from the islands of Borneo and Sumatra) and you and me. The order Carnivora (carnivores) are carnivorous mammals of various sizes with teeth adapted for feeding on meat. Their fangs are especially long and sharp, their fingers are armed with claws, and the brain is quite well developed. Most are terrestrial, but semi-aquatic, aquatic, semi-arboreal, and underground species are also known. This order includes bears, raccoons, martens, mongooses, civets, foxes, dogs, cats, hyenas, seals, and others. Pinnipeds are sometimes isolated in an independent order Pinnipedia. These are predatory animals, highly specialized for life in the water, but still forced to come to land to breed. Their limbs resemble fins, and their fingers are connected by a swimming membrane. Their normal position on land is recumbent; external ears may be absent, the dental system is simplified (they do not survive food), the hairline is often reduced. Pinnipeds are found in all oceans, but dominate in cold areas. There are three modern families: Otariidae (eared seals, i.e. fur seals, sea lions, etc.), Odobenidae (walruses) and Phocidae (true seals).

Order Cetacea (cetaceans) - these are whales, porpoises, dolphins and animals close to them. They are mammals highly adapted to an aquatic lifestyle. The shape of the body is similar to that of a fish, the tail carries horizontal fins that serve to move in the water, the forelimbs are transformed into flippers, no external traces remain of the hind limbs, and the body is normally hairless. The detachment is divided into two suborders: toothed whales (Odontoceti), i.e. sperm whales, beluga whales, porpoises, dolphins, etc., and baleen whales (Mysticeti), whose teeth are replaced by baleen plates hanging from the sides of the upper jaw. Representatives of the second suborder are very large: they are smooth, gray, blue whales, minke whales, humpback whales, etc. Although it has long been believed that cetaceans evolved from four-legged land mammals, until very recently paleontological evidence this was not the case: all known ancient forms already looked like modern ones and did not have hind limbs. However, in 1993 a small fossil whale named Ambulocetus was discovered in Pakistan. He lived in the Eocene, i.e. OK. 52 million years ago, and possessed four functional limbs, representing an important link between modern cetaceans and their four-legged terrestrial ancestors. Most likely Ambulocetus came out on land, like modern pinnipeds. Its legs are quite developed, but, apparently, were rather weak, and this ancient whale moved on them in the same way as sea lions and walruses do. Order Sirenia (sirens) are highly specialized aquatic mammals that are not able to live on land. They are large, with heavy bones, a tail-fin flattened in a horizontal plane, and forelimbs transformed into flippers. No traces of the hind limbs are visible. Modern representatives of the detachment are found in warm coastal waters and rivers. The genus Hydrodamalis (sea, or Steller's, cows) is extinct, but relatively recently met in the northern part of Pacific Ocean. Today living forms are represented by manatees (Trichechidae), living in the coastal waters of the Atlantic Ocean, and dugongs (Dugongidae), found mainly in quiet bays of the Red Sea, Indian and South Pacific Oceans. The order Proboscidea (proboscis) now includes only elephants, but it also includes extinct mammoths and mastodons. Modern representatives of the order are characterized by a nose extended into a long, muscular grasping trunk; greatly enlarged second upper incisors forming tusks; powerful columnar limbs with five fingers, which (especially the outer ones) are more or less rudimentary and surrounded by a common cover; very large molars, of which only one is used at a time on each side of the upper and lower jaws. Two types of elephants are common in the tropics of Asia and Africa. The order Perissodactyla (equids) unites ungulates, leaning on a greatly enlarged middle (third) toe. False-rooted and molars in them gradually pass into each other, although the latter are distinguished by massive crowns square in plan. The stomach is simple, the caecum is very large, gallbladder is absent. This order includes tapirs, rhinos, horses, zebras and donkeys. The order Hyracoidea (hyraxes) includes the only family distributed in Western Asia and Africa. Hyraxes, or zhiryaks, are relatively small animals in which the upper incisors grow constantly and are slightly longitudinally curved, like in rodents. Molar and false-root teeth gradually pass into each other; on the front feet, the three middle fingers are more or less the same, the fifth is smaller, and the first is rudimentary; hind legs with three well-developed toes, the first is absent, the fifth is rudimentary. There are three genera: Procavia (rocky or desert hyraxes), Heterohyrax (mountain or gray hyraxes) and Dendrohyrax (tree hyraxes).

The order Tubulidentata (aardvarks) is now represented by a single species, the aardvark, living in sub-Saharan Africa. This medium-sized mammal is covered with sparse coarse hair; its numerous teeth are highly specialized, its ears are large, the first toe on the front paws is absent, but the hind legs have five approximately equal fingers, the elongated muzzle is elongated into a tube, the lifestyle is terrestrial and burrowing. The aardvark feeds mainly on termites.

The order Artiodactyla (artiodactyls) unites animals resting on the phalanges of the third and fourth fingers. They are large, approximately equal to each other, and their ends are surrounded by a hoof. Pseudo-molar and molars are usually well distinguished; the latter - with wide crowns and sharp tubercles for grinding plant foods. The clavicle is missing. Terrestrial lifestyle. Many species belong to the group of ruminants. The living representatives of the order are pigs, hippos, camels, llamas and guanacos, deer, deer, buffaloes, sheep, goats, antelopes, etc.

The order Pholidota (lizards, or pangolins) includes animals that are probably closely related to the edentulous: they are devoid of teeth, and their body is covered with scales. The single genus Manis comprises seven well-separated species. The order Rodentia (rodents) is the richest in species and individuals, as well as the most common group of mammals. Most species are small; large forms include, for example, beaver and capybara (capybara). Rodents are easily recognizable by the nature of their teeth, which are adapted for cutting and grinding plant foods. The incisors of each jaw (two each above and below) are strongly protruding, chisel-shaped and constantly growing. Between them and the molars is a wide toothless gap - diastema; fangs are always absent. Various species of rodents are terrestrial, semi-aquatic, burrowing or arboreal. This squad includes squirrels, gophers, mice, rats, beavers, porcupines, guinea pigs, chinchillas, hamsters, lemmings and many other animals. The order Lagomorpha (lagomorphs) includes pikas, hares and rabbits. Its representatives are most numerous in the Northern Hemisphere, although they are distributed more or less everywhere. They were absent in the Australian region, where they were brought by white colonists. Like rodents, they have two pairs of large, protruding, chisel-shaped incisors, but there is an additional pair on top, located directly behind the front. Most species are terrestrial, but some American forms are semi-aquatic. The order Macroscelidea (jumpers) includes animals that have long been classified as insectivorous (order Insectivora), but are now considered a completely separate line of evolution. Jumpers are distinguished by well-developed eyes and ears, as well as an elongated muzzle, forming a flexible, but not able to fold proboscis. These features help them find food - various insects. Jumpers live in African semi-deserts and bushes.
Scientific and technical encyclopedic dictionary - (animals), class of vertebrates. Includes oviparous, or cloacal, mammals (first animals) and viviparous mammals (true animals). The first mammals descended from animal-like reptiles, apparently at the beginning of the Triassic or ... Modern Encyclopedia

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AT primary school you need to create different presentations that are designed to develop children. One of the topics of such a presentation is about what animals are mammals. Consider the main representatives.

Presentation on the theme of mammals for children

Bats and bears, monkeys and moles, kangaroos and whales - all these animals belong to the group of mammals, man is also a mammal, as well as most domestic and farm animals - cats, dogs, cows, sheep, goats, etc. In total, there are about 4,500 species of mammals on our planet.

strange mammal

This amazing mammal - the giant anteater - lives in the forests of South America. It feeds exclusively on ants and termites. The anteater breaks insect nests with sharp claws and licks the prey with a long sticky tongue that stretches 60 centimeters in length!

Whales, dolphins and seals are aquatic mammals. Unlike other animals, they do not have hair, and a thick layer of subcutaneous fat protects them from hypothermia.

miniature creatures

One of the most small mammals- . This Mexican leaf-bearer, for example, is no larger than a bumblebee (about 2 centimeters).

Good girl!

The brain of mammals is much better developed than that of all other animals. The smartest living creatures after humans are monkeys. Some of them use the simplest tools: for example, chimpanzees get termites from their nests with a stick.

For comparison

The blue whale is the largest mammal on Earth. Even such a land giant as an elephant looks very small in comparison (see the picture below).

MAMMALS AND THEIR BABY

Mammals are the only animals that feed their young with milk. Babies are born completely helpless and require constant care. A baby chimpanzee, for example, stays with its mother until the age of six.

baby giant

The blue whale, the largest mammal on Earth, also gives birth to the largest cub: the length of the newborn reaches 6-8 meters. The female whale has very nutritious milk, so the baby grows quickly.

oviparous mammals

Some mammals lay eggs, which then hatch into young. One of these unusual animals is living in Australia. It has a bird-like beak and webbed feet. Platypus babies suck milk by licking it off their mother's fur.

marsupials

Kangaroo and koala belong to marsupials. Their cubs are born incompletely formed and continue to develop in a special bag on the mother's stomach. Here the babies suckle milk and stay until they can take care of themselves.

1. A newborn kangaroo gets into your pocket

2. In his pocket he sucks mother's milk

3. The baby is in the pocket until it is covered with hair and can not take care of itself

Caring for offspring

Most mammals take care of their young for some time after birth. Babies, like this cheetah, are usually completely dependent on their mother - she feeds them and protects them. When the cubs grow up, the mother teaches them to hunt and avoid danger.

This material can be used when answering children's questions about animals, as well as about which animals are mammals. In elementary school, this material will be like a presentation on the topic of mammals. Children, having become acquainted with this concept as mammals, presenting their presentation in the class, will have to tell in their own words everything that they have learned. Therefore, do not forget to give your child not only to read our article, but also to retell what he will remember.

Dolphins and bears, moles and bats, elephants and humans - all these animals belong to the class of mammals. Mammals are a class of vertebrates characterized by some unique features by which they can be distinguished from other animals. The main distinguishing features are live birth (except for the oviparous subclass, to which the platypus belongs) and the feeding of offspring with milk.

There are other characteristic features.

Mammals have a diaphragm, a four-chambered heart and have such a property as warm-bloodedness - they are able to regulate their body temperature. Mammalian metabolism controls heat production, and evaporation through the sweat glands cools the body. This makes it possible for mammals to maintain a constant body temperature, regardless of the temperature of the external environment.

The middle ear also has a special structure, in which three bones are distinguished- anvil, hammer and stirrup, they are involved in the conversion of sound waves into nerve impulses. Another characteristic feature of mammals is that in them the base of the skull is connected in a special way with the cervical vertebrae, of which there are always seven in all mammals (both in a giraffe and in a small mouse).

The presence of hair that covers at least some part of the body at some stage of life is also a unique feature of mammals. Mammals feed their young with milk produced by the mammary glands. The mammary glands, like hair, are a feature uniquely found only in mammals.

Mammals appeared over two hundred million years ago during the Jurassic period. The first mammals were small, shrew-like creatures that hunted insects at night. For 130 million years, mammals remained small and survived in a world ruled by reptiles, primarily dinosaurs. But about 65 million years ago there was a catastrophic climate change - the dinosaurs died out, like almost two-thirds of all animals of that time. And mammals survived, thanks to the ability to regulate their own body temperature, and settled throughout the planet.

There are about 5,400 species of mammals in the world today., which are extremely diverse in size, shape and adaptability to the environment. They inhabit all continents and occupy a wide variety of ecological niches: on land (meadows, swamps, forests) and in water (rivers, seas and oceans), in soil and air, in gorges and on mountain tops, in polar regions and deserts. Mammals have a wide variety of sizes: from a few centimeters (bumblebee bat) to several tens of meters (large blue whale).

The most famous orders of mammals are marsupials (kangaroos), insectivores (hedgehogs), bats (bats), rodents (ground squirrels), carnivores (wolf), pinnipeds (seals), cetaceans (dolphins), artiodactyls (hippos), odd-toed ungulates (rhinos), and and finally, primates (humans).

I must have been skipping biology class just when my classmates were studying mammals. Because for a long time I could not clearly answer even myself who belongs to this class. I felt ashamed, and I began to make up for the lost program.

Who are mammals

Mammals are those living organisms that feed their offspring with their milk. The class of mammals is incredibly huge and contains more than 5,000 species. Mammals can live:

• on the land;
• in water;
• underground;
• in the air.

Mammals can be domestic and wild. They can also adapt to any climatic conditions. To do this, nature to help gave them the opportunity to maintain body temperature by sweating or evaporating through the mucous membranes (we saw how dogs breathe through their mouths when it's hot). And in the cold season they are protected by wool, fur or hair. For comparison, in reptiles and fish, scales serve for these purposes, and in birds, feathers.

For clarity, I will give an example of those animals that are mammals: dogs, cats, kangaroos, hedgehogs, elephants, bats, whales, giraffes, rodents, hares, monkeys, horses, lions, wolves.

In 1996, the first cloned mammal, Dolly the sheep, was born. She lived only 7 years.

By the way, people also belong to the class of mammals.

A hallmark of mammals

All animals belonging to the class of mammals have developed all the senses: sight, smell, hearing, touch, taste. Also, mammals have a good memory, are capable of analyzing their actions, are able to distinguish colors and always recognize themselves in the mirror.

One more interesting feature this group is the presence of claws. Note that the hooves of horses and cows are also claws. Only modified ones. Claws help animals to get food, climbing trees and rocks, to defend themselves from enemies (by striking with a hoof or a sharp fingernail).

And for such bulky animals as an elephant, a rhinoceros and a hippopotamus, a horn shoe (hoof-claw) serves as a kind of “hook” when climbing a mountain path.

Quite difficult: different scientists have their own views on which animals belong to a particular order, superorder, clade, group, and all other complex terms that biologists use when unraveling the branches of the tree of life. To simplify the classification a bit, in this article you will discover alphabetical list and the characteristics of the orders of mammals, with which most scientists agree.

Afrosoricidae and insectivores

The order of mammals formerly known as insectivores ( insectivora), has undergone great changes in recent times, dividing into two new orders: insectivores ( Eulipotyphia) and afrosoricides ( Afrosoricida). In the last category are two very obscure creatures: the bristly hedgehogs from southern Africa and the golden moles from Africa and Madagascar.

common tenrec

To the squad Eulipotyphia includes hedgehogs, flint-toothed, shrews and moles. All members of this order (and most afrosoricides) are tiny, narrow-nosed, insectivorous animals whose bodies are covered with thick fur or spines.

Armadillos and edentulous

Nine-banded armadillo

The ancestors of armadillos and edentulous first arose in South America about 60 million years ago. Animals from these orders are characterized unusual shape vertebrae. Sloths, armadillos and anteaters, which belong to the superorder edentulous ( Xenarthra) have the most sluggish metabolism of any other mammal in existence. Males have internal testicles.

Today, these animals are at the edge of the mammal class, but at the time, they were among the largest organisms on Earth, as evidenced by the five-ton prehistoric sloth Megatherium, as well as the two-ton prehistoric armadillo Glyptodon.

rodents

spiny mouse

The most numerous order of mammals, consisting of more than 2000 species, includes squirrels, dormice, mice, rats, gerbils, beavers, ground squirrels, kangaroo jumpers, porcupines, striders and many others. All of these tiny, furry animals have teeth: one pair of incisors in the upper and lower jaws? and a large gap (called a diastema) located between the incisors and molars. The incisors grow continuously and are constantly used to grind food.

hyraxes

Daman Bruce

Hyraxes are fat, short-legged, herbivorous mammals that look a bit like a hybrid of a domestic cat and a rabbit. There are four (according to some sources, five) types of hyraxes: tree hyrax, western hyrax, Cape hyrax and Bruce's hyrax, all of which come from Africa and the Middle East.

One of the strangest features of hyraxes is their relative lack of internal temperature regulation; they are warm-blooded, like all mammals, but at night they gather in groups to keep warm, and during the day they warm up in the sun for a long time, like reptiles.

Lagomorphs

Even after centuries of study, scientists are still not sure what to do with hares, rabbits and pikas. These small mammals are similar to rodents, but have some important differences: lagomorphs have four, rather than two, incisors in the upper jaw, and they are also strict vegetarians, while mice, rats and other rodents, as a rule, are.

Lagomorphs can be identified by their short tails, long ears, slit-like nostrils that they can close, and (in some species) have a pronounced tendency to move by hopping.

Caguana

Malayan woolly wing

Never heard of kaguans? And this wave is possible, because on our planet there are only two living species of woolly wings that live in the dense jungles of Southeast Asia. Kaguanas have a wide skin membrane that connects all the limbs, tail and neck, which allows them to glide from one tree to another, at a distance of about 60 m.

Ironically, molecular analysis has shown that caguanas are the closest living relatives of our own order of mammals, the primates, but their rearing behavior is most similar to marsupials!

cetaceans

The detachment includes almost a hundred species and is divided into two main suborders: toothed whales (including sperm whales, beak-winged, killer whales, as well as dolphins and porpoises) and baleen whales (smooth, gray, dwarf and striped whales).

These mammals are characterized by their flipper-like forelimbs, reduced hind limbs, streamlined bodies, and a massive head that extends into a "beak". The blood of cetaceans is unusually rich in hemoglobin, and this adaptation allows them to stay submerged for long periods of time.

Odd-toed ungulates

Compared to their equivalent artiodactyl cousins, they are a rare order consisting exclusively of horses, zebras, rhinos and tapirs - only about 20 species. They are characterized by an odd number of fingers, as well as a very long intestine and a single-chamber stomach containing specialized ones that help digest tough vegetation. Oddly enough, according to molecular analysis, equid mammals may be more closely related to carnivores (order Carnivores) than to artiodactyl mammals.

Monotreme or oviparous

These are the most bizarre mammals on our planet. Two families belong to: platypus and echidna. The females of these, and do not give birth to live young. Monotremes are also equipped with cloacae (one hole for urination, defecation and reproduction), they are completely toothless and have electroreceptors, thanks to which they can sense weak electrical signals from afar. Scientists believe that monotremes from an ancestor living in, which preceded the split of the placental and marsupials hence their uniqueness.

Pangolins

steppe lizard

Also known as pangolins, pangolins have large, horny, diamond-shaped scales (composed of keratin, the same protein found in human hair) that overlap and cover their bodies. When threatened by predators, these creatures curl into tight balls, and if threatened, they exude a foul-smelling liquid from their anal glands. Pangolins are native to Africa and Asia, and are almost never found in the Western Hemisphere except in zoos.

artiodactyls

Mountain goat

These are placental mammals that have developed third and fourth fingers, covered with a thick horny hoof. Artiodactyls include fauna such as cows, goats, deer, sheep, antelopes, camels, llamas, and pigs, which is about 200 species worldwide. Almost all artiodactyls are herbivorous (with the exception of omnivorous pigs and peccaries); some members of the order, like cows, goats and sheep, are ruminants (mammals equipped with additional stomachs).

Primates

pygmy marmoset

It includes about 400 species and in many respects its representatives can be considered the most "advanced" mammals on the planet, especially in terms of the size of their brains. Non-human primates often form complex social units and are capable of using tools, and some species have dexterous hands and prehensile tails. There is no single feature that defines all primates as a group, but these mammals share common features such as binocular vision, hairline, five-fingered limbs, fingernails, developed cerebral hemispheres, etc.

jumpers

short-eared jumper

Jumpers are small, long-nosed, insectivorous mammals native to Africa. Currently, there are about 16 species of jumpers, which are grouped into 4 genera, such as proboscis dogs, forest jumpers, long-eared jumpers and short-eared jumpers. The classification of these small mammals has been a matter of debate; in the past, they have been presented as close relatives of mammalian ungulates, lagomorphs, insectivores, and arboreal shrews (recent molecular evidence indicates a relationship with elephants).

Bats

Spectacled flying fox

Members of the order are the only mammals that are able to actively fly. The order Chiroptera includes about a thousand species, divided into two main suborders: Megachiroptera(winged) and Microchiroptera(the bats).

fruit bats also known as flying foxes, have a large body size relative to bats, and eat only fruit; bats are much smaller and their diets are more varied, ranging from pasture blood, insects to flower nectar. Most bats, and very few fruit bats, have the ability to echolocate - that is, pick up high-frequency sound waves from their environment to navigate dark caves and tunnels.

Sirens

The semi-marine mammals known as pinnipeds (including seals, sea lions, and walruses) belong to the order Carnivores (see below), but dugongs and manatees belong to their own order, Sirens. The name of this unit is associated with the sirens from Greek mythology. Apparently starving Greek sailors mistook dugongs for mermaids!

Sirens are characterized by their lobed tails, almost vestigial hind limbs, and muscular forelimbs, thanks to which they control their bodies underwater. Although modern dugongs and manatees are small in body size, members of the recently extinct family of sea cows may have weighed up to 10 tons.

marsupials

An infraclass of mammals that, unlike placental mammals, do not carry their young in the womb, but incubate them in specialized pouches after an extremely short interval of internal gestation. Everyone is familiar with kangaroos, koalas and wombats, but opossums are also marsupials, and for millions of years the largest marsupials on Earth lived in South America.

In Australia, marsupials have managed to displace placental mammals for most of the year, with the only exceptions being jerboas that made their way from Southeast Asia, as well as dogs, cats and livestock introduced to the continent by European settlers.

Aardvarks

Aardvark

The aardvark is the only living species in the order Aardvark. This mammal is characterized by its long snout, arched back and coarse coat, and its diet consists mainly of ants and termites, which it obtains by tearing open insect nests with its long claws.

Aardvarks live in forests and grasslands south of the Sahara, their range extends from southern Egypt to the Cape of Good Hope, in the south of the continent. The closest living relatives of the aardvark are artiodactyls and (somewhat surprisingly) whales!

Tupai

indonesian tupaya

This order includes 20 species of tupai, which are native to the tropical forests of Southeast Asia. Representatives of this order are omnivores, and consume everything from insects to small animals, and flowers such as. Ironically, they have the highest brain-to-body ratio of any living mammal (including humans).

Predatory

Brown bear

Without which no documentary about nature would be complete, it is divided into two large suborders: feline and canine. Felines include not only representatives (such as proboscis, they are divided into only three species (or two according to some sources): African bush elephant, African forest elephant and Indian elephant.

However, elephants so rare at present have a rich, including not only their ancestors and mastodons from, but also distant relatives, such as dinotheres and gomphotheres. In case you haven't noticed, elephants are characterized by their large size, flexible and long ears, and prehensile trunks.